YouTube’s algorithm has long promoted videos attacking gun violence victims, allowing the rightwing conspiracy theorist Alex Jones to build a massive audience. But when a not-for-profit recently exposed Jones’ most offensive viral content in a compilation on YouTube, the site was much less supportive – instead deleting the footage from the platform, accusing it of “harassment and bullying”.

Media Matters, a leftwing watchdog, last week posted a series of clips of Jones spreading falsehoods about the 2012 Sandy Hook elementary school massacre, a newsworthy video of evidence after the victims’ families filed a defamation lawsuit against the Infowars host. But YouTube, for reasons it has yet to explain, removed the video three days after it was published, a move that once again benefitted Jones, who is now arguing that the defamation suit has defamed him.

The video was censored for several days, but reinstated Monday after the Guardian’s inquiry and backlash on social media. Still, the case offered yet another stark illustration of the way tech companies and social media algorithms have failed to distinguish between fake news and legitimate content – while continuing to provide a powerful platform to the most repugnant views and dangerous propaganda.

“This just shows the capriciousness and arbitrariness by which they are enforcing these standards,” said Angelo Carusone, the president of Media Matters.

Jones, who has faced numerous lawsuits accusing him of spreading harmful misinformation, has skyrocketed to international fame by fueling a range of conspiracy theories that suggest high-profile mass shootings in America may have been “false flags” or hoaxes, in which the government and “crisis actors” staged the tragedies to push new gun laws.

Francine Wheeler, the mother of Ben Wheeler, 6, who was killed at Sandy Hook, at a recent gun violence forum held in Washington. Photograph: UPI / Barcroft Images

Those quotes are critical now that Jones, in the face of litigation, is alleging that the families’ lawsuit has accused him of making statements he never actually said.

“There was an actual news component to this,” said Carusone, noting that the high-profile student activists from Parkland, Florida had also been sharing the video.

YouTube told Media Matters the video was “flagged for review” and that the company determined it violated “harassment and bullying” policies. Media Matters also received a “strike”, a preliminary penalty that can lead to an account being altogether shut down.

YouTube declined to answer questions about the video and has not explained whether Jones or his associates flagged the video or if the company considered the rightwing commentator to be a harassment victim.

After Media Matters wrote about the censorship and the Guardian inquired, YouTube reinstated the video.A spokesperson said in an email: “With the massive volume of videos on our site, sometimes we make the wrong call. When it’s brought to our attention that a video or channel has been removed mistakenly, we act quickly to reinstate it.”

Media Matters noted that dozens of Sandy Hook videos were still permitted on Jones’ YouTube page, including some the watchdog had used in the compilation. Videos labeled “Crisis Actors Used at Sandy Hook!”, “Sandy Hook was a Total False Flag!” and “Retired FBI Agent Investigates Sandy Hook: MEGA MASSIVE COVER UP” all remained live on Jones’ channel on Monday.

Jones videos have had a long-term impact, Carusone noted. “Years later, parents of these students are still receiving attacks and threats.”

The incident has also served as a reminder that tech companies like Google and Facebook have, in the face of pressure from conservatives, worked to show they are unbiased, Carusone said.